You are trying to dig your way out of your own little hole, but you are still clearly wrong on most points.

Firstly, you have no idea what @lucy_farmer  or any other individual is selling. You don't know if that is their only account, or their principal account, and you have no way of knowing how and why any seller came into possession of the items they are selling.

Secondly, there is no tax liability for selling off your own personally owned items, even of these were acquired by means of bequests. (There are one or two exceptions, but in general, this is the case, especially for the vast majority of genuine private sellers.)

Thirdly, very few collectors will have receipts for every item in their collection. Keeping receipts, if anything, would more likely be a feature of a business seller. Some of my thousands of records were purchased by me well over fifty years ago; many others were gifts. Of course there will be no receipts for these. That is the nature of collections, and is generally accepted, although it is a question which may well be asked.

The case of purchasing a large box of records, keeping some, and then selling the rest, would be trading, and may require to be reported, depending on the sums involved. Selling a genuine collection, however, would not. (Again, if it were a discrete collection, it may be treated as one item for CGT purposes, but this is rare.)

The majority of your post is simply defensive nonsense. You've been caught out baselessly scare-mongering, and instead of bowing out gracefully, you have decided to double down. This  does not reflect well on you.